Communication terminal and wireless sensor network system

1. A sensor node communication terminal comprising: a sensor operable to collect sensor information at a location where the sensor is installed, the sensor collecting the sensor information in autonomous timing; a control unit connected to the sensor, the control unit operable to execute calculation processing of the sensor information collected by the sensor; a memory connected to the control unit; a wireless transmission/reception unit connected to the control unit; an antenna connected to the wireless transmission/reception unit, the antenna operable to transmit wirelessly first wireless transmission data, comprising the sensor information or a result of the calculation processing of the sensor information and to receive second wireless transmission data from a host, said host being configured to collect the first wireless transmission data and to control the sensor node; a power supply unit connected to the control unit; and a timer connected to the control unit, the timer adapted to supply a timer count value used for a timing control of the sensor node, wherein: the sensor node communication terminal is operable such that when the first wireless transmission data is transmitted in the autonomous timing from the antenna to the host, the sensor node provides, to the host, after transmission of the first wireless transmission data, a reception window indicating a predetermined time period during which the sensor node can receive the second wireless transmission data from the host, and if no second wireless transmission data is transmitted from the host to the sensor node during the reception window, or if the second wireless transmission data transmitted from the host to the sensor node is a control signal, the sensor node closes the reception window and is shifted to a sleep mode, and wherein a period of the sleep mode is determined on the basis of the timer count value supplied from the timer, and wherein after expiration of said period, the sensor node will initiate a next transmission of the next first wireless transmission data.

2. The sensor node communication terminal according to claim 1 , wherein the first wireless transmission data transmitted from the antenna to the host comprises a flag indicating whether or not the sensor node continuously executes reception waiting.

3. The sensor node communication terminal according to claim 2 , wherein the sensor node provides a reception waiting time period after transmitting the first wireless transmission data to the host, wherein if the second wireless transmission data transmitted from the host to the sensor node is a data request signal, the sensor node transmits third wireless transmission data to the host in accordance with the data request signal after closing the receiving window, without being shifted to the sleep mode.

4. The sensor node communication terminal according to claim 2 , wherein a determination factor for determining whether or not the sensor node continuously executes the reception waiting is time or information equivalent to time.

5. The sensor node communication terminal according to claim 2 , wherein a determination factor for determining whether or not the sensor node continuously executes the reception waiting is information regarding number of times.

6. The sensor node communication terminal according to claim 2 , wherein a determination factor for determining whether or not the sensor node continuously executes the reception waiting is information regarding a matching determination result between the collected sensor information and a determination criterion previously determined.

7. The sensor node communication terminal according to claim 2 , wherein a determination factor for determining whether or not the sensor node continuously executes the reception waiting may be information regarding a matching determination result between the collected sensor information in addition to sensor information collected until now and a determination criterion previously determined.

8. The sensor node communication terminal according to claim 1 , wherein the sensor node provides a reception waiting time period after transmitting the first wireless transmission data to the host, wherein if the second wireless transmission data transmitted from the host to the sensor node is a data request signal, the sensor node transmits third wireless transmission data to the host in accordance with the data request signal after closing the receiving window, without being shifted to the sleep mode.

9. The sensor node communication terminal according to claim 1 , further comprising a timer clock which executes a substantially time adjustment of the timer when misoperation of the timer occurs.

10. The sensor node communication terminal according to claim 1 , wherein the sensor node includes a talk-after-listen mode function for detecting a presence or absence of communications from the host immediately after transmitting the first wireless transmission data.

11. A host communication terminal comprising: a control unit; a memory connected to the control unit; a wireless transmission/reception unit connected to the control unit; and an antenna connected to the wireless transmission/reception unit, wherein the wireless transmission/reception unit comprises an RSSI unit configured to measure the received signal strength indication of the received electromagnetic wave, wherein the control unit comprises a master rate unit configured to instruct change of the communication rate with respect to a side of the plurality of the sensor nodes according to claim 1 in accordance with the received signal strength indication measured in the RSSI unit, wherein the host communication terminal receives first wireless transmission data from the plurality of sensor nodes through wireless communications, collects sensing data included the received first wireless transmission data, and transmits second wireless transmission data for instructing change of a communication rate specified with respect to the plurality of the sensor nodes in accordance with a received signal strength indication of a received electromagnetic wave.

12. The host communication terminal according to claim 11 , wherein the host communication terminal transmits the second wireless transmission data to the plurality of sensor nodes during only a predetermined time period after the respective sensor nodes transmit the first wireless transmission data to the host communication terminal.

13. A wireless sensor network system comprising: a plurality of sensor nodes; and a host operable to receive constantly or periodically first wireless transmission data separately transmitted from the individual sensor nodes, wherein the individual sensor nodes can receive a second wireless transmission data separately transmitted from the host side during only a predetermined time period after transmission of the first wireless transmission data is completed, wherein each sensor node comprises: a sensor operable to collect sensor information at a location where the sensor is installed, the sensor collecting the sensor information in autonomous timing; a control unit connected to the sensor, the control unit operable to execute calculation processing of the sensor information collected by the sensor; a memory connected to the control unit; a wireless transmission/reception unit connected to the control unit; an antenna connected to the wireless transmission/reception unit, the antenna capable of wirelessly transmitting first wireless transmission data comprising the sensor information or a result of the calculation processing of the sensor information and to receive second wireless transmission data from a host, said host being configured to collect the first wireless transmission data and to control the sensor node; a power supply unit connected to the control unit; and a timer connected to the control unit, the timer adapted to supply a timer count value used for a timing control of the sensor node, wherein: the wireless sensor network system is operable such that when the first wireless transmission data is transmitted in the autonomous timing from the antenna to the host, the sensor node provides, to the host, after transmission of the first wireless transmission data, a reception window indicating a predetermined time period during which the sensor node can receive the second wireless transmission data from the host, and if no second wireless transmission data is transmitted from the host to the sensor node during the reception window, or if the second wireless transmission data transmitted from the host to the sensor node is a control signal, the sensor node closes the reception window and is shifted to a sleep mode, and wherein a period of the sleep mode is determined on the basis of the timer count value supplied from the timer, and wherein after expiration of said period, the sensor node will initiate a next transmission of the next first wireless transmission data.

14. The wireless sensor network system according to claim 13 , wherein when various kinds of sensor information collected at a substantially same time in the plurality of the sensor nodes is transmitted to the host by wireless communications, timings from the collection of the various kinds of sensor information to the transmission to the hosts through the wireless communications are changed among the plurality of the sensor nodes, and thereby a collision of wireless signal data can be avoided, in the plurality of the sensor nodes.